Precision high-speed broach



Sept. 5, 1967 R. J. MEFFERD PRECISION HIGH-SPEED BROACH Filed May v27, 1966' 2 Sheets-Sheet Segr. 5, 1967 R.'J. MEFFERD PRECISION HIGH-SPEED BROACH Filed May v27, 1966 2 Sheets-Sheet 2 INVENTOR @VJ ME'FFEQD United States Patent O M 3,339,255 PRECISION HIGH-SPEED BROACH Roy J. Meterd, 219 W. Myrtle, Laurens, Iowa 50554 Filed May 27, 1966, Ser. No. 553,458 10 Claims. (Cl. 29 95.1)

This invention relates to broach assemblies, and more particularly to a broach assembly of the type employing a central mandrel and a plurality of helically-shaped cutters revolving in planetary fashion around said central mandrel.

A main object of the inlvention is to provide a novel and improved high-speed precision broach assembly which is relatively simple in construction, which operates with high precision and accuracy, and which is adjustable to provide a desired finish diameter.

A further object of the invention is to provide an improved high-speed broach assembly which involves inexpensive components, which is durable in construction, which is easy to adjust, which is smooth in operation, and which enables an internal bore such as the inside surface of tubing, or the like, to be finished to a high degree of accuracy.

A still further object of the invention is to provide an improved high-speed broach assembly of the type employing a central driving spindle or mandrel with a plurality of cutters rotating around said spindle or mandrel in planetary fashion, the assembly being provided with means for assuring and facilitating the discharge of chips or loosened material from the assembly duringoperation so that there will ibe no interference by such chips or loosened material with the cutting action of the device, the device being provided with means for adjusting its diameter so as to compensate for changes in effective size of the cutters due to re-grinding or re-sharpening thereof or to take care of varying manufacturing tolerances.

Further objects and advantages of the infvcntion Will become apparent from the 'following description and claims, and from the accompanying drawings, wherein:

FIGURE l is a side elevational view, partly in vertical Y cross-section, showing the lower portion of an improved broach assembly constructed in accordance with the present invention.

FIGURE 1a is a side elevational view, partly in vertical cross-section, showing the upper portion of the broach assembly of FIGURE 1.

FIGURE 2 is a transverse vertical cross-sectional view taken substantially on the line 2 2 of FIGURE 1.

FIGURE 3 is a transverse vertical cross-sectional view taken substantially on the line 3 3 of FIGURE 1.

FIGURE 4 is a transverse vertical cross-sectional view taken substantially on the line 4 4 of FIGURE 1.

FIGURE 5 is a transverse vertical cross-sectional wiew taken substantially on the line 5 5 of FIGURE la, with certain parts omitted and showing the cross-sectional shape of the upper supporting housing of the assembly of the broach device of FIGURES 1 and la.

FIGURE 6 is a transverse vertical cross-sectional view taken substantially on the line 6 6 of FIGURE 1a.

FIGURE 7 is an end view of the broach device taken substantially on the line 7 7 of FIGURE la.

Referring to the drawings, 11 generally designates a broach assembly constructed in accordance with the present invention. The assembly 11 comprises a central main spindle 12 which is rotatably-supported at its opposite j ends in the respective end housings 13 and 14 and which is also rotatably-supported at its mid-portion by a supporting assembly 15, presently to be described.

The spindle 12 is formed at its lower end with a reduced journal shaft portion 16 which is rotatably-supported in a central bore 17 provided in the lower housing 3,339,255 Patented Sept. 5, 1967 ICC 13 and is journaled in said Ibore by means of yroller bearings 18. An end thrust bearing assembly, comprising a ball-bearing unit 19 is provided on the outer portion of the reduced shaft element 16, being retained by a `bearing cup member 20 threadedly-engaged on the outer end portion of shaft element 16 and locked in position by means of a set screw 21 provided thereon.

At its top end the spindle 12 is formed with a shaft portion 22 which is journaled in an adjustable sleeve member 23 threadedly-engaged centrally in the end wall of the top housing member 14, the shaft portion 22 being rotatably-supported in the sleeve 23 by means of roller bearings 24 provided in an annular raceway recess 25 formed in sleeve 23. An annular ball-bearing thrust assembly 26 surrounds the sha-ft portion 22 adjacent the inner end of sleeve 23. The outer end of sleeve 23 is formed with the enlarged flange or head 27 which is recessed as shown at 28 to receive another ball-bearing assembly 29 retained in the recess 28 by a retaining nut 30 threadedly-engaged on shaft portion 22 and locked in place `by a set screw 31 provided thereon. The inner ball-bearing unit 26 bears against abutment shoulders 32 provided on the shaft portion 22, so that the sleeve member 23 is freely rotatable on shaft portion 22 but is retained against axial displacement relative to said shaft portion by the respective opposite end ,ball-bearing assemblies 26 and 29. However, because of the threaded engagement of sleeve 23 with the top housing member 14, rotation of the sleeve member 23 will move the top housing member 14 in an axial direction relative to spindle 12, namely, parallel to the axis of spindle 12, for a purpose presently to be described.

The top end of shaft portion 22 is provided with a suitable driving head 33 adapted to be drivingly-coupled to suitable drive means for rotating the spindle 12.

Journaled in the respective housings 13 and 14 and spaced around the spindle or mandrel 12 are a plurality of rotary cutters 34, said cutters 'being arranged in diametrically-opposite pairs, the cutters being provided with helical cutting edges 35 with the opposite cutters being of opposite hand. Thus, in the pair of cutters shown in FIGURES l and la, the upper cutter is a right-hand thread, and the lower cutter is a left-hand thread. The cutters 34 are provided with upwardly-convergent frustoconical center bearing portions 36 which engage with rolling contact on a frusto-conical collar member 74 provided on spindle 12, as will be presently described.

It will be noted that the pitch of the threads of the cutters 34 decreases upwardly, being smallest at the top ends of the cutters, for the purpose of preventing the cutters from grooving the bore in which they are operating, namely, from following a riding pattern. The cutter edges are provided both with a small amount of back clearance, as shown at 38, as well as with a small amount of positive clearance, as shown at 39.

Each cutter 34 is provided at its -bottom end with a reduced journal shaft portion 4t)` which is rotatablysupported in a bore 41 provided therefor in the housing 13 by means of roller Ibearings 42, as is clearly shown in FIGURE l. Each cutter is formed integrally adjacent the lower journal shaft portion 40 thereof with a pinion gear 43 which meshes with a drive pinion gear 44 integrally-formed on the central mandrel or spindle 12. The gears 43 and the central drive gear 44 are housed in the shell or skirt portion 45 of housing 13. A plurality of bores 46 are formed in the main relatively thick end wall 47' of housing 13, said bores 46 being evenly distributed and being located between respective shafts 40, as shown in FIGURE 2, the bores 46 serving as escape passages for any small chips which may have entered the space adjacent gears 43, 44 during use. The bores 46 allow the small chips and cutting fluid to drain out of said space.

Large chips are excluded by a bronze chip guard 46 provided above said gears, the mandrel 12 and cutters 34 extending through suitable apertures provided in said chip guard 46'.

At the top end of the tool, the `cutters 34 are integrallyformed with pinion gears 47 which mesh with a drive gear 48 integrally-formed on the mandrel or spindle 12 sfubjacent the upper end `shaft portion 22 thereof. The cutters 34 are formed with upwardly-convergent frustoconical neck portions 49 subjacent the pinion gears 47 which slidably and rotatably-engage with a downwardlyconvergent frusto-conical collar member 50 integrallyformed on the mandrel or spindle 12. It Will be seen from FIGURE la that the frusto-conical collar 50 has a taper which is substantially opposite to that of the taper of the frusto-conical neck portions 49 of the respective cutters 34. It will further be seen that due t-o the wedging cooperation between the neck portions 49 and the collar member 50, upward movement of the cutters relative to the spindle o-r mandrel 12, namely, movement to the right of the cutters, as viewed in FIGURE la, causes the cutters to move outwardly or to expand whereas, movement in the opposite direction contracts the working outer diameter of the revolving cutters. As will presently be explained, this may be accomplished by suitably adjusting the sleeve 23.

The top housing member 14 is provided with a skirt or shell portion 52 which surrounds the meshing gears 47 and 48 as well as the cooperating neck elements 49 and the collar member 50. Ball-bearing units 53 are provided between the upper shank portions 54 of the cutters and the integral -pinion gear elements 47 thereof, the ball-bearing units 53 bearing against the relatively thick main wall 55 of housing 14, as shown in FIGURE la. Shank portions 54 terminate in reduced stud elements 57 on which are threadedly-engaged retaining nuts 58, ball-bearing units 59 being engaged on the studs 57 between the nuts 58 and the outside end surface of main wall 55. The retaining nuts 58 are provided with set screws 60 to lock them in position on the studs 57. It will thus be seen that the shank portions 54 are locked against axial movement relative to the end wall 55 of housing 14, being retained against longitudinal movement, but being freely rotata-ble between the ball-bearing assemblies 53 and 59. As shown in FIGURE 6, the longitudinal bores 62 in wall 55 which receive the shank portions 54 are elongated radially or are substantially oval in shape, to permit inward and outward adjustment of the top ends of the cutters in accordance with the coaction of tapered neck members 49 with the oppositely-tapered frusto-conical collar member S resulting from the adjustment of the sleeve 23 relative to housing 14.

The top surface of the ange 27 is provided with a 'suitably calibrated adjustment scale 64 which may be rotated relative to an index mark 65 provided on the end wall 55 to establish a desired position of adjustment of sleeve 23. As above-mentioned, rotation of the sleeve 23 by means of flange 27 causes the housing 14 to be moved axially, thereby moving the tapered neck members 49 along the frusto-conical surface of the collar mem-ber 50, thereby moving the upper end portions of the cutters 34 inwardly or outwardly, in accordance with the direction of rotation of the nut member 27.

The lower end shaft elements 40 of the `cutters have sufficient play to allow the aforesaid adjustment inwardly or outwardly of the upper end portions of the cutters. The intermediate tapered bearing portions 36 of the cutters are yielda-bly-retained, as will be presently described, in the intermediate supporting assembly 15, and this assembly is provided with spring means acting on the frusto-conical intermediate cutter bearing portions 36 to urge them inwardly. Thus, the intermediate bearing assembly 15 comprises four identical mating segments 70 formed with arcuate notches 71 which define a circular opening when the segments are brought together in the manner illustrated in FIGURE 4, said circular opening rotatably-receiving the spindle or mandrel 12 immediately above a frusto-conical collar element 74 formed on the member 12.. The segments 70 are provided with marginal flanges 75 which are arcuatelyshaped adjacent the frusto-conical neck portions 36 of the cutters and which engage the portions 36 to rotatablysupport same in rolling contact with the frusto-conical periphery of the collar element 74, as shown in FIGURE l. The segments 70 are formed with mating semicircular notches 77 which dene circular openings when the segments are brought together, said circular openings rotatably-receiving the frusto-conical neck portions 36, as shown in FIGURES l and 4. U-shaped spring clips 78 are lockingly-engaged over the abutting outer end portions of the arms of the segments 70, the spring clips 78 being provided with inturned locking anges 79 which are received in transverse grooves provided therefor in the outer surfaces of the segment arms, whereby the four spring clips 78 resiliently-secure the four mating segments 70 together on the mandrel 12 with the respective frustoconical neck portions 36 received in the apertures dened lby the respective pairs of opposing semicircular notches 77, the frusto-conical neck portions 36 being resilientlyheld in rolling contact with the periphery of the collar member 74.

It will be noted that the angle of slope of the frustoconical collar member 74 with respect to the axis of mandrel 12 is substantially less than that of the collar member 50, and is sufficiently different from the angle of inclination of the periphery of collar member S0 to assure that the neck portions 36 will remain in rolling contact with collar member 74 throughout the range of inward or outward adjustment of the top ends of the cutters.

Main wall 55 of housing 14 is provided with a radial set screw 91 to lock sleeve 23 in adjusted position.

It will be noted that the cutters 34 have a slight taper from top to bottom, being of maximum diameter at their top ends, since the tool must be of larger outer diameter at its top end than at its bottom end, and the bottom outer diameter of the tool must be smaller than the prefinished size of the bore to be finished. As above-mentioned, by rotating the sleeve 23 in one direction, the effective outside diameter of the top end of the tool may be increased, whereas rotating the sleeve 23 in the opposite direction reduces the effective outside diameter of the top end of the tool.

As will be readily apparent, when the mandrel or spindle 12 is rotated by a suitable drive means, the upper gear portion 48 thereof drivingly-engages with the pinion gear elements 47 of the cutters 34 so that the cutters rotate in a planetary fashion around the mandrel 12. The lower mandrel gear 44 meshingly-engages with the integral pinion gears 43 on the cutters, providing a stabilizing action, as well as operating in the same manner as the upper gear 48 to deliver driving force to the lower ends of the cutters. Therefore, in operation, the mandrel 12 is driven by its drive means while the tool is fed downwardly into a bore to be reamed at a suitable rate, causing the helical cutting edges 38 of the cutters 34 to ream the bore to the desired inside diameter. The cutting action is accompanied by the feeding of cutting uid downwardly through the tool and bore, most of the resultant chips and the fluid passing downwardly along the sides of the tool through side channels, shown at 90. The cutting uid can, therefore, be furnished with suflicient volume to cause the chips and loosened material to be washed out of the bore and down past the tool as the cutting action continues, whereby there will be minimum interference by chips or loosened material with the cutting action.

The center supporting assembly 15 is employed where the cutters 34 are relatively long and where the tool is used with bores of considerable length where a large amount of material is to be removed from the inside of the bore. Where a relatively short tool can be employed, namely, where the length of the bore is relatively small, the center supporting assembly may be omitted, since in the case of short cutters 34 there would be no necessity for intermediate support thereof.

The adjusting iiange 27 may be suitably calibrated, for example, in thousandths-of-an-inch, in accordance with the changes in outer working diameter of the top end of the cutter assembly produced by rotating the sleeve 23. Thus, as shown in FIGURE 7, the scale 64 may be calibrated in thousandths-of-an-inch. The numerical values provided on scale 64 will, of course, be in accordance with the outward movements produced by the cooperation of the frusto-conical collar element 50 with the abutting frusto-conical surfaces of the neck elements 49 as the cutters are moved longitudinally relative to the mandrel 12 responsive to the rotation of the sleeve 23.

Experience has shown that the broaching tool of the present invention can be operated with either all righthand or all left-hand cutters, or any combination of the two. Also, instead of employing cutters whose pitch changes toward the top, the tool may employ cutters of two or more different pitches (constant for their entire length) to accomplish the same purpose. For example, one cutter may have a pitch of 4-threads per inch, another may have a pitch of S-threads per inch, another may have a pitch of 4-threads per inch, and the last cutter may have a pitch of 6-threads per inch. Other possible combinations may be similarly employed.

While a speciiic embodiment of an improved broach assembly has been disclosed in the foregoing description, it will be understood that various modifications within the spirit of the invention may occur to those skilled in the art. Therefore, it is intended that no limitations be placed on the invention except as defined by the scope of the appended claims.

What is claimed is:

1. A broach assembly comprising a rotary mandrel, housing means at the top and bottom end portions of the mandrel, means rotatably-supporting the top and bottom end portions of the mandrel in said housing means, elongated cutter means arranged substantially parallel to said mandrel, means rotatably-supporting said cutter means in said housing means, and means gearingly-Coupling said mandrel to said cutter means.

2. The broach assembly of claim 1, and wherein said cutter means comprises at least two elongated cutters located on opposite sides of the mandrel, said cutters being formed with helical cutting edges of opposite sense.

3. The broach assembly of claim 2, and wherein said helical cutting edges decrease in pitch toward the top ends of the cutters.

4. The broach assembly of claim 3, and wherein said means gearingly-coupling the mandrel to the cutters comprises top and bottom drive gears on the mandrel and top and bottom pinion gears on the cutters meshing with said drive gears.

5. The broach assembly of claim 4, and wherein said cutters taper downwardly in diameter from their top ends toward their bottom ends.

6. The broach assembly of claim 5, and means to vary the spacing between the top ends of the cutters and the top portion of the mandrel.

7. The broach assembly of claim 1, and means to adjust the outer working diameter of the cutter means adjacent the top end portion of the mandrel.

8. The broach assembly of claim 1, and wherein the cutter means comprises at least two elongated cutters located on opposite sides of the mandrel, said cutters being formed with helical cutting edges, and means to adjust the spacing between the top end portions of the elongated cutters.

9. The broach assembly of claim 8, and wherein the adjusting means comprises a conical collar element rigidly-secured on the top portion of the mandrel, frustoconical neck portions on the cutters of opposing convergency with respect to and in Wedging and rolling contact with said collar elements, and means to adjust the cutters longitudinally relative to the mandrel.

10. The broach assembly of claim 2, and a frustoconical collar element on the intermediate portion of the mandrel, frusto-conical neck portions on the cutters of opposite convergency with respect to and in rolling engagement with said collar element, and resilient retaining means bearing on said neck portions and urging said neck portions toward said collar element.

No references cited.

HARRISON L. HINSON, Primary Examiner. 

1. A BROACH ASSEMBLY COMPRISING A ROTARY MANDREL, HOUING MEANS AT THE TOP AND BOTTOM END PORTIONS OF THE MANDREL, MEANS ROTATABLY-SUPPORTING THE TOP AND BOTTOM END PORTIONS OF THE MANDREL IN SAID HOUSING MEANS, ELONGATED CUTTER MEANS ARRANGED SUBSTANTIALLY PARALLEL TO SAID MANDREL, MEANS ROTATABLY-SUPPORTING SAID CUTTER MEANS IN SAID HOUSING MEANS, AND MEANS GEARINGLY-COUPLING SAID MANDREL TO SAID CUTTER MEANS. 